Screens are now being expanded downhole to take the place of a gravel packing operation. Several U.S. Patents reveal the technology used to expand screens downhole. A few examples are U.S. Pat. Nos. 5,901,789; 6,315,040 and 5,366,012. In running screens to the desired position in the wellbore, there was a problem of screen plugging before expansion could take place. The fact that the screen openings were exposed also precluded forced circulation to remove wellbore debris before expanding the screen.
In the past, screens that were not expanded were covered with a movable sleeve. In U.S. Pat. Nos. 5,443,121 and 5,617,919, a movable sleeve was used to facilitate distribution of gravel outside the screen. U.S. Pat. No. 5,355,956 shows a cover sleeve over a screen with sacrificial plugs in holes that are eventually removed after the screen is positioned by introducing a chemical to dissolve the plugs. Finally, U.S. Pat. No. 3,099,318 shows a sheath or belts around a multi-layered filter material to compress it for run in. When the assembly is in place a chemical is introduced to remove the sheath or bands and allow the filter layers to expand to their natural thickness. The sheath or rings for compression can also be released by defeating a lock when the screen is in the desired position downhole. Compression of the screen is required so that it can run downhole where it can later expand and work more efficiently, according to this reference.
The present invention allows the openings in the screen to be closed during run in and downhole fluid circulation or reverse circulation. When the screen is expanded, the covering on the screen allows flow by a variety of techniques. The covering can be ripped off due to expansion or openings in the covering can develop due to the screen expansion, to name a few techniques. These and other aspects of the present invention will be more readily appreciated by one skilled in the art from a review of the description of the preferred embodiment and the claims, which appear below.